Filling material of polyester fibers

ABSTRACT

A filling material of polyester fibers is formed by garnetting staple length fibers to a web then spraying a resinous bonding agent on the web and curing the resin to bond the constituent fibers. The resin is present in diminishing quantities through the web from one face to the other. A plurality of such webs may be used to form a layered structure which has a high degree of filling support weight along with a desirable degree of softness.

United States Patent 1151 3,660,222 Fleming, Jr. et al. 1 1 May 2, 1972s41 FILLING MATERIAL OF POLYESTER 3,449,486 6/1969 Contractor et a1..161/170 x FIBERS 3,373,455 3/1968 Kaplan ....161/152 X 2,949,3948/1960 Rodman..... ....16l/156 X [72] inventors: David AlexanderFleming, Jr., Wilming- 2 9 0 570 4 19 1 Cook et 3] 1 52 X ton; GilbertDouglas Rawlings, Hockessin, both of Del.

[73] Assignee: E. l. du Pont de Nemnurs and Company, Primary n r-Ro ertF. Burnett Wilmington, Del. Assistant Examiner-Mark A. Litman An H dP. Wt,J 221 Filed: Apr. 1, 1969 War es 1211' Appl. No.: 811,819 [57]ABSTRACT A filling material of polyester fibers is formed by garnetting[52] 11.5. CI ..l61/l56, 156/295, 161/157, Staple ng h fibers to a wethen spraying a resinous bonding 161/166, 161/170 agent on the web andcuring the resin to bond the constituent [51] Int. Cl. ..B32b 5/14, B32b5/28 fibers. The resin is present in diminishing quantities through [58]Field of Search ..l61/152, 156, 157, 164, 166, the web from one face tothe other. A plurality of such webs 161/169, 170 may be used to form alayered structure which has a high degree of filling support weightalong with a desirable degree [56] References Cited of softness.

UNITED STATES PATENTS 2 Claims, 7 Drawing Figures 3,461,026 8/1969Schick "161/156 X PATENTEUMAY 2 I972 3,660,222

SHEET 10F 2 FIG. 1

INVENTORS 7 DAVID ALEXANDER FLEM'NG JR.

GILBERT DOUGLAS RAWLINGS BY fi o 1W ATTORNEY PATENTEDMM 2m? 3,660,222SHEET 20F 2 ,F|G.4 Fl [-16.6

I00 90M a DISTA (PERCENT) INVEN 5 DAVID ALEXAND FLEMING GILBERT DOUGLRAWLINGS ATTORNEY FILLING MATERIAL OF POLYESTER FIBERS BACKGROUND OF THEINVENTION This invention relates to fibrous nonwoven articles and, moreparticularly, to lightweight, resilient, high-bulk materials suitablefor cushioning and insulating.

Fibrous materials of natural origin, such as cotton, have long been usedas fillings in such articles of commerce as seat cushions, paddings andinsulated garments. Because such natural fibers lack a high degree ofresilience, it is customary to combine them with metal springs ormaterials such as foam rubber to compensate for this shortcoming.Crimped synthetic fibers such as polyethylene terephthalate are known tohave a very high degree of resilience and, combined with their low cost,mildew resistance, and odorand allergy-free attributes, they would beexpected to give excellent performance as filling materials. Fillingmaterials of synthetic fibers have been produced by methods well knownin the art of processing natural fibers including carding or garnettingthe staple-length fibers to a web which is cross-lapped to the desiredthickness onto a moving apron. Although being soft to the touch, suchfilling materials lack a high degree of support bulk, i.e., the abilityto maintain a high proportion of original thickness under an appliedload, and when they are in use in cushioning, their constituent fibershave a tendency to disassociate and the cushion tends to mat afterrepeated use. More recently, researchers have found that the addition ofbonding resin to bond the fibers at their cross-over points in the webproduces improved support bulk and prevents the fibers from migrating.It is commercial practice today to cross-lap webs and spread resin onthe surface of the layered structure. Because of the improvementsrealized by the use of bonding resin, researchers have been eager tofind methods for thoroughly and uniformly impregnating webs of syntheticfibers so that each and every fiber of the web is covered with resin.Such thoroughly impregnated webs may be made of bi-component fibers,i.e., sheath/core fibers having a core of synthetic polymer and a sheathof another polymer of lower meltingpoint. Thus, in effect, the sheath isthe bonding resin in these structures. Such filling materials made withthese thoroughly impregnated webs have a high degree of support bulk butlack softness. Thus, it seemed that softness and support bulk wereincompatible and either one or the other could be had, not both. It hasnow been discovered that both may be attained and the present inventionprovides a filling material of synthetic fibers having the desirablecombination of softness and support bulk.

SUMMARY OF THE INVENTION This invention provides a bulky, lightweight,resilient, easily compressible, fibrous filling material of densitybetween about 0.003 and 0.04 gm./cc., comprising a bonded laminate of aplurality of thin fibrous webs of crimped linear polyester fibers, eachof said thin webs having a gradation of resin concentration on theindividual fibers which extends diminishingly from the top web-face tothe bottom web-face, i.e., present in diminishing quantities from oneface to the other. The majority of fibers within the volume bounded bythe length, width and half the depth, (the half depth being one-half ofthe web thickness measured by a perpendicular from the top web-face) ofeach of said thin webs are bonded at their cross-over points by a resinand the above described volume contains at least 70 percent, by weight,of the entire amount of resin n the web.

The product is produced by a process by a process wherein a lightweightweb of linear polyester fibers is conveyed by a first moving flatsurface and continuously discharged therefrom onto a second flat,substantially horizontal, moving surface and stacked or lapped onto saidsecond surface by pendulous movements of said first moving surface. Aresinous liquid is applied to the thin web by spraying one of its faceswhile it is supported by the said second surface, in such a manner as tohave a gradation of resin concentration extending diminishingly from thesprayed face to the opposite face, and thereafter curing the resin tobond a substantial number of the constituent fibers at their cross-overpoints.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be betterunderstood by reference to the accompanying drawings wherein,

FIGS. 1 and 2 are schematic elevational views of an apparatus used forproducing the filling material of the invention showing sequentially themethod used in forming a laminate structure,

FIG. 3 is a schematic elevational view of a transverse crosssection ofthe new filling material,

FIG. 4 is a schematic elevational view of a transverse crosssection of afilling material of the prior art subjected to a load,

FIG. 5 is a similar view of another structure of the prior art,

FIG. 6 is a similar view of a filling material of the present invention,and

FIG. 7 is a graph showing a preferred gradation of resin concentrationin the practice of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. 1 and 2wherein like parts have been given the same numeral of reference,crimped polyester staple-length fibers 1 are fed to the main cylinder 2of the carding section of a conventional garnett. They are worked by theworker rolls 3, stripped from the worker rolls and returned to the maincylinder by stripper rolls 4, removed from the main cylinder byconventional doffer roll 5, and transported in web form 7 on travelingapron 8 driven by rollers and 8b. The thin web then passes to thecross-lapper comprising traveling aprons 9 and 10 driven by rollers 9a,9b, 10a and 10b, respectively. After passing between the aprons, the webis discharged onto flat apron 11 which travels in a directionperpendicular to the plane of the paper. The cross-lapper makespendulous backand-forth movements in the direction of the arrows whilethe web is discharged onto the apron in such a manner that the web islayered or cross-lapped on traveling apron 11. In accordance with thepresent invention, the cross-lapper is fitted with frame 16 bearingspray nozzles 17 and 18 which connect to a pressurized resin supply andswitching means (not shown) for starting and stopping the nozzles in apredetermined manner. Although only two nozzles are shown it is to beunderstood that more than one nozzlemay be used on each side. As thecross-lapper reaches one end of its period, one set of microswitches isactivated and turns nozzles 18 off and 17 on, thus as the cross-lapperswings back and forth, nozzles 17 and 18 alternately spray resin ontothe laid web. Thus, as shown in FIG. 1, the cross-lapper moves fromright to left while spray nozzle 17 sprays resin onto the web laid downby the previous traverse of the cross-lapper and nozzle 18 is off. InFIG. 2, the cross-lapper has just begun to move from left to right andnozzle 17 is off while nozzle 18 sprays resin onto the web laid down bythe previous traverse of the cross-lapper. Thus, preferably, the resinis always sprayed ahead of the cross-lapper. Inthis manner, each thinweb is sprayed on one surface and, in accordance with the presentinvention, there is a gradation of resin concentration extendingdiminishingly from the sprayed web face tothe opposite face.

After the webs are sprayed with resin and stacked as taught hereinabove,the resin is cured. This may be accomplished conveniently in accordancewith conventional procedures by passing the structure through an oven bymeans of a conveyor apron. The temperature is chosen to be consistentwith the curing temperatures of the particular resin used. After curingthe resin, the nonwoven product may be heated even further to developmore support bulk. It has been found especially when working withhelically crimped fibers that an additional heating process attemperatures from to 200 C. for a period from 2-8 minutes produces anextremely high degree of support bulk.

Other well-known methods of making and depositing a thin web in layerson a moving apron may be used.

In the foregoing process, the webs which have been crosslapped lie flatand have substantially no wrinkles in the layered structure. If theprocesses of the prior art were modified wherein resin would be sprayedonto the vertical unsupported portion of the web as it issued from thecross-lapper, the polyester fibers, unlike cotton fibers, would flyapart and the web would billow and become disordered. The devices of theprior art even modified as such may be satisfactory-with natural fiberssuch as cotton but with fibers such as staple-length polyester they failto produce a coherent, flat, resin-impregnated fibrous structure.

The term polyester fibers includes fibers as defined in 1960 Supplementto Book of ASTM Standards" part at page 5 3. Linear polyesters useful inthe practice of this invention include linear terephthalate polyesterssuch as polyethylene terephthalate, polyethyleneterephthalate/isophthalate, polyethylene terephthalate/S-(sodiumsulfo)-isophthalate (97/3), and poly (p-hexahydroxylyleneterephthalate). Preferably, the polyester is polyethylene terephthalate.

The term filling support weight? (FSW) is used herein to define thesupport-bulk of a nonwovenstructure. The meaning of the term will bebetter understood by reference to the following testing procedure: Anunbleached muslin-ticking (commonly used in seat-cushion construction),measuring 22 by 22 by 3.5 inches (55.9 X 55.9 X 8.9 cm.), is stuffedevenly with some of the filling material to be tested. The cushion isplaced on a table top or other flat surface and its thickness (under noload) is measured. A fiat, rigid, round disc of 50 square inches (322.5cm?) surface-area is placed on top of it. Weights are placed on the discuntil the total weight of the loaded disc is;62.5 pounds (28.4 kg.). Thethickness under load is measured. Filling material is evenly added to orwithdrawn from the ticking and the above process is repeated until itsthickness under load is just 30 percent of its thickness under .no load.At this point, the maximum thickness (thickness under no load) of thefilled ticking is at least 4 inches (10.2 cm.), and is preferably 6 to 8inches (15.2 to 20.3 cm.). The filling is then removed from the tickingand weighed. The weight of the filling is reported as FSW. It is readilyseen that a filling material having good support-bulk has low FSWvalues, while a filling material having poor support-bulk has high-FSWvalues (e.g., greater than 2 pounds).

Crimp frequency is measured according to the following procedure: Asample of crimped fiber is straightened by applying just enough tensionto do so. The fiber is marked at intervals of 1 inch (2.54 cm.) while inthis condition. The tension is removed and the fiber is allowed toresume its crimped configuration. Crimp frequency is the average numberof peaks per marked interval on one side of the helix axis, in the caseof coiled fiber. A similar measurement is made in the case of a fiberwith sawtooth crimp.

The wet pick-up, i.e., the percent, by weight, of resin emulsion orsolution on the web based on the weight of the unimpregnated web, maybefrom about 20 to 200 percent to insure an adequate resin add-on; i.e.,the percent by weight, of nonaqueous (or non-volatile) ingredients inthe resin mixture based on the weight of the unimpregnated web, of about1.5 to about 50 percent.

The fibers used in accordance with the present invention are crimped.The crimp may be the sawtooth variety produced by a staffer-box crimpershown in US. Pat. No. 2,311,174; Preferably, however, the fibers arecrimped in helical configuration as described in US. Pat. No. 3,050,821and processed as shown in U.S. Pat. No. 3,414,648. The fibers have acrimp frequency of from about 4 to 30'crimps per inch (per 2.54 cm.),and may have a denier of from about I to 40. Preferably, the crimpfrequency is about 9 crimps per inch (per 2.54 cm.) and the denier isabout 4.

The resins used in accordance with the present invention may be chosenfrom the acrylics, melarnines, polyvinylchlorides, polyvinylacetates,polyesters, polyurethanes, ethylene copolymers and others. Preferablythe resin is an aqueous emulsion comprising ethyl acrylate,methylmethacrylate N-methylolmethacrylamide, methacrylic acid and acrosslinking agent. Other additions may be included such as silicones toconfer additional softness to the fibers. Flame retardant resin systemssuch as polyvinylchloride with tris 2,3- dibromopropylphosphate may beused.

It is important that the fiber and the resin be chosen so that a wickingeffect, wherein by capillary action or a similar wetting phenomenon, theresin is drawn into and through the web to effect uniformdistribution ofresin throughout the thickness of the web, is avoided. Cotton fibersproduce the undesirable wicking effect.

The new fibrous filling material may be produced in any length, width,or thicknessuUsually from about 4 to about 70 and preferably about 12layers of web are used to make up the new structures, each layer beforeimpregnation being of density from about 0.0008 to 0.01 g./cc. Each thinweb, before impregnation with resin, may be from 0.04 to 0.15 ounce perft. (1.22-4.57 mg./cm.) weight and is preferably 0.08 to 0.13 ounce perft. (2.44 to 3.96 mg./cm."). The density of the new fibrous structuremay be from about 0.003 to 0.04 g./cc.

Contrary to teachings of the prior art-where uniform resin penetrationthrough the webs was desired, it has now been found, surprisingly, thata gradation of resin concentration is desirable not only for a highdegree of support bulk but for aesthetic qualities such as softnessofnon-woven structures to be used as filling materials. This may be seenin FIGS. 4-6, which are explained later in Example H.

The distribution of resin in a web may be determined by cutting anindividual web from the laminated structure. This web is then bisectedby cutting through the plane running through the center of itsthickness. The amount of resin present in each portion may be determinedby dissolving the resin and weighing it, or dissolving the fiber andweighing it and subtracting this from the total weight of theresin-impregnated web. Altemately, the amount of resin may be determinedby visual inspection of photomicrographs of the crosssection of the webto be analyzed. Use of colored dye in the resin composition facilitatesthis determination. Similarly, the amount of resin in any volume of theweb may be measured once the required volume is separated from the web.

The filling material of the present invention, composed of layered webs8 (FIG. 3), has on-one side of the interface between the layered webs anarea containing fibers which are heavily coated with resin and on theotherside an area con taining fibers which contain less resin. FIG. 3shows a struc ture of the present invention wherein webs 8 are shownstacked one on top of the other, each web having an area 19 near saidinterface which is coated heavily with resin and an area 20 whichcontains less resin. Contrary to prior art methods 1 in which thoroughresin-impregnation of webs is desired, such is not desired in thepractice of this invention. In the prior art, especially in usingcellulosic fibers, it was found that the recovery properties of thesefibers are improved by using a resin which would cross-link thecellulosic molecules. Thus, it was important that each and every fiberin the web be contacted with the cross-linking" resin and, obviously,thorough impregnation of the web with resin was desirable. In theproduct of the present invention, it is important that there be agradation of resin on each constituent web.

The preferred gradation of resin concentration is shown in FIG. 7. is agraph showing the distribution of resin in an individual web of acomposite filling material. The ordinate shows the cumulative amount ofresin, in weight percent, in the various sections marked on the abcissawhich shows distance in percent from the bottom (0 percent) face to thetop face (sprayed face) of the web. A completely uniform distribution ofresin from bottom to top with no gradation of concentration, such asoccurs in products of the prior art, would be represented by line Awhile a web containing resin onits top face as a surface layer only,there being no resin penetration into the web, would be represented bythe line B. In accordance with the present invention, the resindistribution falls within the area bounded by curves C and D, i.e.,OCPDF. Preferably, the distribution follows curve E. Thus, the volumebounded by the length, width and half depth, the half depth beingoneihalf of the web thickness measured by a perpendicular from the topweb face (sprayed face) contains at least 70 percent of the total weightof resin on the web.

In preparing the new filling material, the individual webs are stackedone on top of the other. For illustration, the face of an individualweb, which contains the greatest amount of resin (sprayed face) will becalled A and the opposite face will be called B. In stacking the webs ontop of each other to make the new filling material, it is preferred tohave an ABAB arrangement although other arrangements such as ABBA arewithin the scope of the present invention. An additional resin coatingof the complete structure may also be made.

The invention is further illustrated by the following examples ofpreferred embodiments which are not intended to be delimitative.

EXAMPLE I Approximately 200 pounds (91 kg.) of commercially available,2.0 in. (5.1 cm.), 4.25-denier-per-filament polyethylene terephthalatestaple having a crimp frequency of approximately 9.5 crimps per inch(per 2.54 cm.) and containing about 0.3 percent, by weight, TiO isproduced substantially as taught in U.S. Pat. No. 3,414,648 and fed to aconventional doubledoffer gamett. The gamett is set to produce a 0.09oz./ft. (2.7 mg./cm.) web at the rate of 125 lbs./hr. (57 kg./hr.) andfeeds to a cross-lapper. The machinery is arranged substantially asshown in FIG. 1. The thin web, which is about 60 inches (152.4 cm.)wide, and of about 0.125 lbs./ft. (0.002 g./cm. density, discharges fromthe cross-lapper, which swings back and forth, onto apron 11 whichtravels in a direction parallel to the plane of the web in thecross-lapper at approximately ft./min. (3.05 meters/min.) The webdischarges from the cross-lapper at an angle with respect to the apronto form a 45-inch 1 14 cm.) filling material. The web is sprayed byresin from eight spray guns, four on each side of the cross-lapper andeach discharging resin toward the apron and onto the laid webs as shownin the drawings. The spray guns spray the web ahead of the cross-lapper,and, as described above, the spray guns spray alternately. The orificeof each nozzle is about 0.026 inch (0.066 cm.) in diameter and thesupply pressure is about 60 psig (4,218 g./cm. Each nozzle is designedto spray resin in a fan-like pattern 15-inches (38.1 cm.) wide onto theweb. Thus, four nozzles cover the 60-inch wide 152.2 cm.) web thatadvances onto the floor apron. The wet pick-up of resin is about 65percent and the resin add-on is about 15 percent. The resin compositioncomprises a 23 percent aqueous emulsion comprising 46-parts ofethylacrylate, 48-parts methylmethacrylate, 47-partsN-methylolmethacrylamide, 1- part methacrylic acid and a cross-linkingagent. A transverse cross-section of the layered fibrous structurecontains 10 layers of the thin webs, each layer having a gradation ofresin concentration through its thickness so that the fibers within thevolume bonded by the length, width and half depth, the half depth beingone-half the web thickness measured by a perpendicular from the sprayedface of each thin web is coated with resin at the fiber cross-overpoints and contains about 75 percent, by weight, of the entire amount ofresin on the, thin web.

The structure is dried in an oven at approximately 196 C. for 2 minutes.The resulting structure is bulky, soft, resilient, lightweight and has adensity of about 0.41 lbs/ft. (0.0066 g./cm.

The laminated fibrous structure is then heated at approximately 196 C.for 4 minutes and is shown to have a surprising amount of softness,support bulk, and resilience, a combina tion unequalled by any whollyfibrous filling material known today. The product has an FSW of about1.80 pounds (0.82 kg). Fibrous filling materials of the prior art withsimilar softness have FSW values of about 2.2 pounds (1 kg.), or more.

EXAMPLE II This example shows two filling materials of the prior art andcompares these with a filling material produced substantially as shownin Example I, in regard to conformability.

Reference will be made to FIGS. 4-6 to describe the bulk and softnesstests of the filling materials of this example.

A fibrous filling material is produced substantially as shown in ExampleI with the exception that no binder resin is used and there are eightlayers of the webs instead of 10 layers. No heat treatment is performed.Six of these layered materials (8 in FIG. 4) are stacked one on top ofthe other to make a filling material comprising 48 layers of thin webs.A solid brass cylinder 20 measuring 4 inches 10.2 cm.) in diameter by1.25 inch (3.18 cm.) in height is placed on a flat bench top 21. Asample of the filling material measuring 1 1 X 22 inches (27.9 X 55.9cm.) is placed on the cylinder and a 1-inch (2.54 cm.)- thick flat board22 measuring 12 by 24 inches (30.5 X 61 cm.) is placed on top of thefilling material. A 12.4-pound (5.73 kg.) weight is placed on the board.The filling material conforms to the shape of the cylinder substantiallyas shown in FIG. 4 where it is apparent that the open space 23 betweenthe cylinder and the first layer of web, is small. Because no heattreatment is used and because no resin binder is used, this fillingmaterial has poor support bulk. Heat treatment such as performed in theprevious example would cause an increase of thickness under the load, ofabout 50 percent.

Another fibrous filling material is produced substantially as describedin the preceding paragraph and tested for confonnability in the samemanner. The fibers of this filling material are composed of two polymersintimately adhered along their length in concentric sheath/corerelationship, the polymer making up the core being polyethyleneterephthalate, the polymer making up the sheath being poly(ethyleneterephthalate/isophthalate) (79/21) having a lower melting point thanthe core component, the fiber being composed of weight percentpolyethylene terephthalate and 15 weight percent poly(ethyleneterephthalate/isophthalate) (79/21). The fibers are 2.5 inches (6.35cm.) long, of 4.2 denier per filament and have a sawtooth crimp of 7.3crimps per inch (per 2.54 cm. In preparing this filling structure, afterthe thin webs issue from the cross-lapper and are cross-lapped to makeup the layered structure, the structure is heat treated at approximately232 C. for approximately 2 minutes to bond some of the fibers at theircrossover points and given another heat treatment at the sametemperature for 8 minutes. The thickness of the layered filling materialis approximately the same as the thickness of the filling material ofthe preceding paragraph. This is a filling material of the prior art.The filling material is tested for conformability in the same mannerwith the same load, as stated in the preceding paragraph and as shown inFIG. 5, although it has a high degree of support bulk, it conforms tothe shape of the cylinder relatively poorly as shown by large area 23 ascompared to the showing of FIG. 4.

Another filling material is produced substantially as shown in Example 1and tested in the same manner as the filling materials of the precedingparagraphs. This web, being produced in accordance with the presentinvention, shows a high level of conformability and a high level ofsupport bulk, substantially as illustrated in FIG. 6. Area 23 is smallshowing the structure is conformable to the shape of an exterior object.In addition to this, the structure supports the load nearly as well asthe structure of FIG. 5. Furthermore, another ad vantage of the presentinvention and a surprising phenomenon is apparent in FIG. 6. Theindividual webs of the laminate, which are closest to block 20, arecompressed more than those which are farthest from block 20. Theadvantage of this in a filling material can be appreciated byvisualizing a sleeping bag having a stick or stone underneath. The userwould not be as much annoyed by the presence of the object, i.e., itspresence would not be transmitted through each layer of web as it wouldbe with materials of the prior art.

What is claimed is:

diminishing quantities through each web from one to the other face,about 75 percent of said resin being contained in onehalf the thicknessof each web as measured from said one face. 2. The filling material ofclaim 1, and said webs fonning a layered structure, said one and saidother faces of adjacent webs being contiguous.

III I! i l

2. The filling material of claim 1, and said webs forming a layeredstructure, said one and said other faces of adjacent webs beingcontiguous.